Since Taiwan is located on the circum-Pacific seismic zone, earthquake occurrence is quite frequent, and strong earthquakes occur quite often as well. According to the Central Weather Bureau's earthquake monitoring information between 1900~1990, the average number of earthquakes in Taiwan is approximately 2,200 per year, of which, approximately 214 can be felt. After the major renewal of the CWB Seismic Network in 1991, the ability of earthquake detection improved drastically. The annual average number of earthquakes recorded from 1991 to 2004 increased to 18,649 (monthly average was approximately 1,554), of which approximately 1,047 were felt. In 1999, Taiwan had the highest number of earthquakes, mainly due to the influence of the Jiji (Chi-Chi) earthquake; there were 49,919 earthquakes, including 3,003 quakes felt. Based on the statistical analysis of catastrophic earthquake information, there have been 96 catastrophic earthquakes since 1900.